The Importance Of Human Centric Lighting In Building Design

Generally, lighting is designed purely for functionality (i.e., allowing us to see to perform a task or to illuminate an area so it can be safely navigated). However, a human-centric lighting (HCL) installation goes far beyond just functionality, it can also provide biological, health and productivity benefits.

People are now spending more time indoors whether it be for work or leisure than our ancestors before us. Studies have shown that this can have a negative effect on people’s wellbeing and natural circadian rhythm. We have a natural circadian rhythm which is in essence our natural 24-hour wake/sleep cycle (which is closely tied into the sun rising and setting).

Studies have shown that a disrupted circadian rhythm can lead to:

• Increased risk of obesity (disrupted circadian can affect the bodies digestive system)
• Increased risk of stroke (due to elevated blood pressure)
• Increased risk of sepsis.
• Increased risk of heart disease.
• Increased risk of depression/mental health issues.

What is HCL? How Does it Work? What are the Benefits?

To understand how HCL works a small biology lesson is required. In 2002 the discovery of a third photoreceptor in the human eye essentially gave birth to the idea of HCL. These photoreceptors (known as “Intrinsically Photosensitive Retinal Ganglion Cells (ipRGC’s)) primary function is to signal light for largely subconscious reflexes such as neuroendocrine regulation and synchronizing daily circadian rhythms to the light/dark cycle. The type of light that produces the most effective light is in the “blue” colour region of the visible light spectrum between 400-500nm-which can increase alertness and reactions and decrease sleepiness.

Neuroendocrine Regulation is essentially the regulation (production, suppression, secretion of bodily hormones) and the ones that are particularly of interest concerning HCL (these hormones are directly linked to the circadian rhythm and well-being) are:

• Cortisol: Known as the stress hormone released by the adrenal glands. This is important for helping your body deal with stressful situations. This hormone plays a vital part in the natural circadian rhythm as it can help control blood sugar levels, regulate metabolism, reduce inflammation, and assist with memory formation.
• Melatonin: Often referred to as the sleep hormone (also known as the darkness hormone), it is primarily released by the pineal glands. It is produced in the evening and peaks around midnight. Melatonin actively promotes healthy sleep (helping the body wind down) and helps enforce the body’s natural circadian rhythm
• Serotonin: This is referred to as “the happy hormone”. It can impact various bodily functions from emotions to motor skills. It can reduce depression, regulate anxiety, and enhance sleep.
• Dopamine: This hormone is responsible for pleasure, alertness & muscle coordination.

As can be seen from the graphic above, Attention spans peak when cortisol is at its highest level and attention spans are at their lowest when melatonin levels are at their peak. Cortisol production is linked to “cool white” light and melatonin production is linked to “warm white” light.

The most beneficial operation of an HCL installation is a cool white light in the mornings and warm white light in the evenings. With a DALI lighting control system, the HCL installation could be configured for various starting times/shifts and offers more flexibility to the installation. The difference between cool white and warm white light can be seen in the graphic below.

In essence, HCL is the art of artificially mimicking the colour temperature of the sun as the day progresses. HCL operates using tunable white luminaires (luminaires that can change their colour temperature as required) combined with a DALI lighting control system. The benefits from HCL can include maximized concentration and energy, improved work performance and productivity, increased motivation & commitment, improved circadian rhythm & quality of sleep as well as increased emotional stability & lowered rates of depression.

How does this play into current electrical and building design? 

Human Centric Lighting is a technology that is growing in popularity worldwide as LED technology becomes more efficient and cheaper. It has applications across various sectors such as offices, educational buildings, healthcare premises and control rooms within data centres and pharmaceutical plants. 

It is still very early days for the application of Human Centric Lighting as research is still in its early stages. What still holds is that wherever possible natural light should be utilised and any additional lighting should compliment this. 

Various building standards are recognizing the importance of the interaction between the end-user and the built environment. One example is the WELL building standard. This Building Standard includes guidelines on illumination that are aimed to minimise the disruption of the body’s circadian system and enhance productivity and now offers credits for human-centric lighting installations.

Buildings are no longer just “one space” they are now a collection of spaces that are used for different purposes and therefore require a diverse pattern of visual environments. A human-centric daylighting approach to lighting will not only improve the quality of spaces in commercial buildings but can also help reduce the payback of these design features. Already, human-centric lighting system costs are decreasing and coupled with the uplift in worker productivity, the payback time in some cases can be reduced dramatically.